The concept of frameless stereotaxy is now emerging in the field of neurosurgery. Frameless stereotaxy involves quantitative determination of anatomical positions on a human body, say for example a human head, based on image data taken from a CT (computed tomography), MRI (magnetic resonance imaging) or other well-known slice scanning techniques. The data from such image scans may be entered into a computer to generate a three dimensional graphic representation of the human head. This is of great value to surgeons, as they may visualize where they will be operating relative to this data field. Surgeons may thus, plan their operations quantitatively prior to actually performing them, based on an anatomy visualization represented by the image data.
To date, the use of stereotactic head frames for fixing and orienting a head is commonplace. For example, see U.S. Pat. No. 4,608,977 issued on Sep. 2, 1986, to Brown and entitled: System Using Computed Tomography As For Selective Body Treatment. Such stereotactic head frames utilize a head fixation device, typically with some form of an index means, that may be visualized in scan slices or image data. Thus, the anatomical image data can be defined relative to the head frame.
Arcuate mounts or probe carriers may be fixed to frames to hold and guide a probe based on the anatomical image data. If use of the head holder and carrier can be limited, patient discomfort can be greatly reduced.
The headholder and localizer still may be used for general neurosurgery where only approximate target positioning is needed. For example, a space pointer may be directed over the anatomy and its position may be quantified relative to the stereotactic image data. The space pointer, analogous to a pencil, might be pointed to a specific location on the anatomy such that the location and the direction of the pointer, subsequently appear, real time, on the computer graphics display of the anatomical data. Such an apparatus has been proposed, using an articulated space pointer with a mechanical linkage. In that regard, see an article entitled "An Articulated Neurosurgical Navigation System Using MRI and CT Images," IEEE Transactions on Biomedical Engineering, Volume 35, No. 2, February 1988 (Kosugi et al), incorporated by reference herein. It would be convenient and effective if the space pointer could be mechanically decoupled or minimally mechanically coupled.
One objective of the present system is to provide a camera apparatus (optical) to visualize a surgical field and relate it via a computer graphics system to stored image data of the patient's anatomy. The relationship between the camera data and the image data is processed to quantitatively represent and indicate surgical instruments such as probes, microscopes, or space pointers in relation to the anatomy image.
Another objective of the present invention is to optically couple a space pointer or other equipment item to accomplish the same objectives as the robotic arm mechanically coupled space pointer, e.g. give ongoing positional correspondence between a location in a patient's brain and the tomographic image. The optical coupling frees the surgeon from sterility questions, provides an obstruction-free device, and avoids the encumbrances of a bulky mechanical instrument.
According to a method of "frameless" stereotaxy as described above, a camera system or navigator consists of a set of cameras viewing a surgical field, in relation to a patient's anatomy. Equipment or anatomy, e.g. probes, a microscope, or other surgical devices may be viewed and tracked by the cameras within the surgical field, and the position of these devices may be quantitatively determined. Various registration, mapping, transformation, or merging schemes may combine the image scan data of the patient's anatomy with camera system data. Various examples are shown and described involving index reference points on anatomy or equipment that may be used to correlate to the image scan data. Natural landmarks, contours, surfaces, or other reference marks are disclosed for combining image scan data of the anatomy with real time physical anatomy or equipment position data.
Other illustrative examples are disclosed for registration between the image scan data (e.g. stored data) and anatomy and equipment data (e.g. real time). The examples given may apply to the field of "frameless" stereotaxy, wherein a head frame or head clamp is placed on the patient's head after the image scanning is done. It may also apply to frame-based stereotaxy, where a head clamp or head frame is placed on the patient's head prior to image scanning. The methods and apparatus and the examples given herein may be used in a variety of fields, including interventive stereotaxy, stereotactic radiosurgery and radiotherapy, or general image processing to relate image data to an apparatus means or surgical or diagnostic equipment environment.